As is well known in aircraft technology, it is abundantly important to prevent gasses escaping from the aircraft engine from migrating into the nacelle and accumulating to the point where the gasses would combust and either cause fires or explosions. It is customary to purge the nacelle so as to avoid such occurrences. A current technique for purging the nacelle is to locate a pump adjacent to the exhaust nozzle and pump the ram air that is contained in the nacelle through exhaust ports located at the tail end of the aircraft. Obviously, this entails pressurizing the stagnated gasses to assure that the proper exhaust flow is maintained throughout the operating envelope of the aircraft. The inclusion of a pumping apparatus results in a heavier support structure than is necessary to attain the structural integrity of the engine parts which increases overall engine weight and hence, incurs an engine operating performance deficit.
In certain installations the pumping system is accommodated in the side wall of the nacelle adjacent to the flaps of the 2-dimensional exhaust nozzle. For example the co-pending patent applications mentioned in above integrate the pumping system in the side walls. In other installations the side walls may not be sufficiently large to accommodate the pumping system.
One type of pump heretofore utilized for this purpose is an ejector pump that utilizes fan discharge air as the primary fluid and dumps the entrained nacelle air directly overboard. The use of fan air for this purpose and in this manner penalizes engine performance as the fan air would otherwise be used for generating thrust.
It is also important in this technology to pump nacelle cooling air at flow rates and pressures sufficient to be entrained into the nozzle gaspath flow for cooling the divergent flap edge pieces. Typically, one of two sources have heretofore been utilized for cooling. One of the sources is the fan air which has sufficiently high driving pressures but is at relatively high temperatures which results in poor cooling and as mentioned above comes at the expense of engine performance. The other source is the ambient air that is entrained in the nacelle which has sufficiently low temperatures that would provide efficient cooling, but its pressure is too low for it to penetrate into the engine's gas path and flow therein.
We have found that we can obviate the problems enumerated in the above paragraphs and obtain sufficient cooling of the flap edge pieces and purging of the nacelle without unduly sacrificing engine performance. This invention contemplates an ejector pump integrated into the divergent flap with a mixing chamber that minimizes utilization of fan air and maximizes use of ambient air to attain sufficient flows at the required pressure level and including means for discretely dumping the cooling air in the gaspath. In addition to the pumping system the entire cooling system including the flow paths are integrated into the convergent and divergent flaps of the exhaust nozzle.